There are a few caveats with this beta, as one might expect: the main one is that you cannot use the sync capability if you already synchronize with an Exchange account, as there can be only one ActiveSync config on the iPhone or iPod touch at any time. Setting up sync with Google will also nuke your local contacts and calendar on the device, so back up before you proceed. Still, this represents a big step forward in the delicate dance of Google services in cooperation with Apple's mobile gear.
If you configure sync for your device, let us know how it goes! Early comments note that the lack of multiple calendar support is a showstopper -- if that applies to you, check out the NuevaSync option. Update: You can apparently sync up to five calendars to the phone, see here for details.